The present invention relates to seals and, in particular, to a seal that retains lubrication between the interface of a spline shaft and a sleeve shaft, which move relative to each other.
The interface between a spline shaft and a sleeve shaft, such as on a driveshaft or propshaft, is typically sealed by a molded boot that is coupled to each shaft. The boot includes flexible joints or ribs that allow expansion and contraction of the boot as the shafts move relative to each other along an axis. One problem with these boots is that they typically require a relatively large volume of space around and along the shafts to provide boots that are capable of extending and compressing as required by the shafts. The large volume of space around the boot ensures that components of the vehicle do not contact or damage the boot during operation of the vehicle.
One problem with these boots is that they can easily be damaged. Another problem is that due to the amount of flex required by the boots, stress cracks may occur, especially as the boot ages. Any damage or cracks may result in dirt and other debris entering the boot, or leakage of lubricant from the boot. Dirt or debris in the boot, or loss of lubricant decreases the durability and life span of the sliding interface between the shafts. Due to the size of the boot, in some applications, the boot may be located in close proximity to high temperature components, and therefore require the use of expensive engineered plastics.
To address the above problems, some manufacturers use more compact seals that function as a dynamic seal. While these seal designs alleviate many problems associated with the molded boot, other problems are created, such as longevity of the seal in retaining lubricant in the interface between the shafts as well as preventing dirt, debris, and other materials from entering the interface between the shafts. These compact seals are typically formed from an elastomeric material and the constant relative movement of the seal against the spline shaft may cause the seal to break down over time.
Another problem with compact seals is obtaining the proper fit of the projections of the seal within grooves on the spline shaft. More specifically, if the engagement between the seal and spline shaft is too tight, the projections will quickly wear. Alternatively, if the engagement is too loose, the projections may have difficultly in wiping dirt and debris free of grooves and ribs on the spline shaft and difficulty in retaining lubricant within the interface.